The invention relates to a piston with a piston skirt having a piston-pin bore.
Pistons with piston skirts for an internal combustion engine in which a piston-pin bore in the piston skirt is introduced as a formed bore are universally known. Because of the loads on the inner surfaces of the piston-pin bore in which the pin which connects the piston to the connecting rod is located, the pin is exposed to extremely high loads in operation because of pin deformation during the motion of the piston. To compensate for the deformation of the piston-pin bore (boss bore) it is known in the prior art (for example, DE 21 52 462 A1, DE 30 36, 062 C2, DE 41 41 279 C2, DE 44 41 450 A1 or DE 102 31 233 A1) to design the boss bore to be oval, circular or cylindrical in segments or sections along the surface line of the piston-pin bore. However, in the transition from a section with one shape to another section with a different shape, transitions result which create a step and which disadvantageously result in an additional load on the boss bore and the pin located therein.
Thus it known from the disclosure DE 21 52 462 or patent DE 27 56 878 C2 that the piston-pin bore widens evenly (approximately trumpet-shaped) in the direction of the piston inner area referenced to the pin axis. In patent DE 30 36 062 C2 it widens only above the bore axis. With these widening shapes of the piston-pin bore in the axial direction of the piston inner area, better seating of the pin on the surface of the piston-pin bore is certainly achieved if the pin deforms when the piston is operating, but because of the demands made on modern combustion engines with respect to fuel consumption and exhaust emissions which must be complied with, resulting in corresponding combustion temperatures and combustion pressures during the operation of the piston in the combustion engine, the total load on the piston-pin bore and piston pin system is still extremely high and support of the piston pin in the piston-pin bore is not optimal.
It would be desirable to provide a piston-pin bore configured as a formed bore for a piston which avoids the disadvantages described above, that is, with which an increased load on the entire piston can be achieved and any additional, or the entire, load on the boss bore/pin system is reduced.